I would like to build a waterproof deck (suitable for living space underneath), using something that looks good, has low maintenance, and fails gracefully if at all. I’m thinking that 12″ to 18″ tiles or stone would work well. I’d prefer not to use a mud base. I’m thinking of the following layup:
Truss joists; plywood (pressure treated if it’s winter during construction); 1/2″ cementious backer board bedded in thinset; membrane bedded in thinset; tile set in thinset. At the edges, I’m thinking I’d attach a strip of backer, fold the membrane over it, and apply vertical trims over that.
My questions are: (1) Is this a good and reliable approach? (2) If so, what membrane? (Intuition suggests something with a bit of stretch. Do I visit the roofing supplier or the tile supplier?) and (3) Is standard sanded grout OK? Assume we freeze occasionally.
Replies
I've never seen a recipe for a waterproof tile deck that did not call for a deck-mud setting bed. I think you need:
-framing with or without slope
-subfloor, does not need to be PT ply.
-sloped mortar bed IF the framing is not sloped, to a drain or other exit point
-membrane (probably chlorolloy)
-deck-mud setting bed on top of chlorolloy without ANY penetrations of the membrane
-tile
The key is getting the membrane wrapped up onto all of the walls and seamed everywhere without any holes through it. Any application of backer board is going to require screws, nails, or staples. Get Michael Byrne's book 'Setting Tile' and check out the shower detail.
Maybe someone else knows more about the use of membranes over backer board as a waterproof installation. I've set a lot of tile,and seen others set a whole lot more, and never seen the applicaiton you describe.
Edited 12/18/2003 5:28:54 PM ET by davidmeiland
The Tile Council of America has tile standards, cutaways, and specs for outdoor exterior tile decks. Order their literature.
In general, you have to build the deck like a shower pan. Sloped mud base at a quarter inch per foot, then a membrane, then a drainage mat, then an additional sloped mud base as a setting bed. This all has to drain somewhere where a scuper of some sort is located.
You may (I am not sure) use a surface applied membrane like Kerdi over a sloped mortar bed, then tile, so only one mud bed. I do not know if Kerdi is approved in an exterior application.
If you are looking for validation to apply CDX to ceiling joists then tile away with marble, you won't get it here. Visit the TCA.
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
Many thanks to Boris and David for your input. I won't do it!
I am intrigued by the idea that it should be possible, and was hoping for a newer and easier technique. But I can't afford to use customers and guinea pigs.
There are some paintable membranes out there, but the substrate and setting bed still have to be pitched, right? Like any roof.Regards,
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934